Balsa Cabinets?

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I was knocking up an experimental HF horn from balsa wood, and it suddenly occured to me that balsa might make a good cabinet material.
Low resonance, intrinsic damping, relatively strong... seems like a possibility.
I know balsa sandwiches have been done, but has anyone tried balsa as the main structure? Obviously finishing might be a problem (fabric of some sort is a possibility), and I don't know what are the largest panels available, but from the illustrations I've seen, the trees can be quite substantial.
Any thoughts?
 
re wood laminate structures

Dear dnsey,

try talking to the folks at the de Haviland aeroplane co.

They used marine ply carcass with balsa wood filler to give a true laminate composite material.

When they first came up with this idea for a fighter the MOD laughed loud and long.

They then realised that there was no more metal to make real aeroplanes so went back to de Haviland and asked them to build the funny wooden plane.

So the de Haviland Mosquito came into being.

Very light very strong resilient to damage and easily repaired when damaged.

So if it was good enough to cause havoc in WW2 then why not today as a cabinet material.

Try it and see.

3-6mm ply outer and inner skin with 15mm balsa inner filler.

Should be interesting. Very light and very stiff with good damping properties.

regards David
 
Don't use it for bass. Or use it for bass and see if you can make it explode... :D

Well, use thick panels for bass, good luck getting them though.

I would want to do some experimentation before saying the material doesn't have a resonance in an important audible range.

$0.02
 
I agree with DAVOhorn. At least as far as strength to weight goes it would be ideal as part of a composite

If you are talking about using it on its own. It has a high strength to weight ratio but you would need to use very thick panels as Stocker mentioned. A broad panel of Balsa will flex quite easily. You could also overcome this by using redioculously extensive internal bracing.

AFAIC the only solid advantage of using balsa for a speaker cabinet it that it is so easy to shape. You can make a sculptured shape out of a solid balsa block using little more than a pen knife and sandpaper.

Besides all this It is actually a good idea to have a cabinet that is reasonably heavy otherwise the divers motor will tend to move the cabinet as well as the air in front of its diaphram!
 
Hi,

it all sounds fairly reasonable.

Composites are well known and its the outer ~15% of
each surface that counts, mechanical performance of the
other 70% doesn't really matter but for balsa ideally the
grain would run surface to surface, though practically its
best to let the grain run along the length of a panel.

So you get a light, strong and very stiff panel, great !
Which you can then damp for a classic BBC style cabinet.

Worked all this out a long time ago and then looked
at the price of balsa wood. Owwwwcccchhhh!!!!!!!!!

:) /sreten.
 
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Joined 2003
As sreten says, the strength is in the skin, not the core. An ideal composite would be a skin of the really thin plywood that modellers use with a balsa core. Yes, I found out about the Mosquito too. And I found out how expensive balsa is. On the other hand, the amount of work that you put into making a pair of loudspeakers is so great that I don't consider the material cost to be, well, material.

Little known fact: The Apollo lunar lander used balsa as a shock absorber on the legs.
 
Try this http://www.jamestowndistributors.com/product;part;33055;process;search;ID;;eclDrill;3249

Ideal as a starting point - thin ply (3 ply or 5 ply) on the exterior and you're good to go - If you laminate with balsa however, you will reduce weight further, and be able to cut using a scalpel (making comstruction more of a kitchen table affair).

I've constructed very small speakers from balsa (in my misspent youth) - they were all charecterised by a very natural 'tone'

I anticipate great results!

Owen
 
dnsey said:
I know balsa sandwiches have been done, but has anyone tried balsa as the main structure?


Are you asking if Balsa alone will work? Because everyone is pushing the composite idea for good reason.


EC8010 said:
the amount of work that you put into making a pair of loudspeakers is so great that I don't consider the material cost to be, well, material.

Aint that the truth.

Balsa is also so easy to work that it almost justifies the cost.
(I know this pobably wasn't your point) :cannotbe:

I still think the weight of MDF is an advantage. Remember we are talking about a speaker cabinet not an aircraft.
The amount of energy passing to the cabinet from both the driver and its backwave is semi dependent on how light as well as compliant and lossy the material is. A light composite not fair as well unless it really is significanly stiffer.
 
The celestion aerolam speakers are fairly lightweight, and I see no reason why the balsa composite should not be as stiff.

The Aerolam speakers were very highly regarded...

Owen

edit - found the celestion reference

In 1983 the revolution was completed by the addition of an aluminium honeycomb cabinet which provided a remarkably high stiffness/weight ratio. The SL600 set new standards at the audiophile end of the market, selling particularly well in Japan, and winning numerous awards around the world.

from http://www.celestion.com/history/1980s.html

Good enough for Japan, good enough for me!

Owen
 
Thanks everyone for your replies.
Yes, Filgor, I was really thinking of using just Balsa, probably cross-laminated for stability and to avoid having to source large panels.
I suspect that it would indeed work well as a composite (I've used expanded polystyrene, which has some similar properties, that way), but I was interested in the surface properties, which hopefully would obviate the need for damping.
(Train of thought: making experimental horn from balsa for convenience - wondered if it needed a 'hard' finish applying to avoid absorption of HF - realised that this was desirable for cabinets - considered possibility of trying it.)
I appreciate the comments regarding weight - I think I'd probably arrange for a sandbag in the base to keep things steady, but I'm not sure to what extent mass is necessary for effective damping.
I'm sure that large slabs of balsa are pricey, but the sammer bits, which would be OK for laminating, seem fairly reasonable. OTOH, I wonder if there are still any scrapyards with old mosquitos...:D
A lot more projects to complete before trying much in this line, but I might have a go at a little cab for a 3" driver just to see how it turns out - unless one of you gets there first, of course:)
 
owen said:
The celestion aerolam speakers are fairly lightweight, and I see no reason why the balsa composite should not be as stiff.
Owen


Absolutely. :nod:

No argument against this at all. I think a well designed, well braced and skinned balsa cabinet is a fantastic DIY alternative to aluminium honeycomb cabinets. I also think that closely spaced bracing of cabinet walls across to opossing walls (and bracing between bracings) will result in a very stiff cabinet. This would be particularly simple and practical to achieve with balsa.

I'm mainly concerned with the significance of the ratio of cabinet mass to the drivers net moving mass... Any ideas as to when, if at all this would become an issue?
 
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Joined 2003
If this was done as an experiment, perhaps using the Fostex FE103, then the mass of the cone compared to the magnet is tiny anyway, and a heavy box always assumes that the basket supporting the magnet is perfectly rigid. Since a popular FE103 modification is to wedge caulking compound between the magnet and the basket, I think we can assume it isn't perfectly rigid. I don't see a problem with a light box.

The SL600 undoubtedly had a heavier cone in comparison to the box...
 
EC8010 said:
If this was done as an experiment, perhaps using the Fostex FE103, then the mass of the cone compared to the magnet is tiny anyway, and a heavy box always assumes that the basket supporting the magnet is perfectly rigid. Since a popular FE103 modification is to wedge caulking compound between the magnet and the basket, I think we can assume it isn't perfectly rigid. I don't see a problem with a light box.

The SL600 undoubtedly had a heavier cone in comparison to the box...


Good call,

I was beginning to think along the same lines as well.

So how much is balsa these days? :D
 
EC8010 said:
Well, I've just looked, and it's not quite as bad as I thought. A strip 100mm x 20mm x 1000mm was £4.95. OK, so it's much more expensive than MDF, but a composite balsa box will be leading edge technology compared to an MDF box.

Good work EC8010!

Still watching Dnsey?

It looks like you could be on to a possible winner here.

In the name of experimentation the cost is negligable.

I'm tempted to give it a go myself. I'm working on a centre channel using 4 mid bass drivers that already has more than enough mass. Only problem is that it might be too front heavy! :rolleyes:
 
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